Recently, for the medical treatment of myocardial infarction and angina pectoris, for example, a method in which a lesion (stenosed part) of the coronary artery is widened by using a balloon catheter is performed. A similar method can be performed for treating a stenosed part formed inside another blood vessel, the bile duct, the trachea, the esophagus, the urethra and other living body lumens as well.
The balloon catheter generally includes an elongated shaft portion and a balloon, which is provided, on a distal end side of the shaft portion while being dilatable in a radial direction. After a contracted balloon reaches a target part in the body via the inside of a thin living body lumen, the stenosed part can be widened by dilating the balloon.
Accordingly, the balloon needs to be thinly contracted until the balloon reaches the target part. JP-A-2003-62080 discloses a method in which the balloon is folded so as to be wound around an outer peripheral surface of the shaft portion in a circumferential direction.
When a balloon is wound around an outer peripheral surface of the shaft portion while being folded, a turned-back portion can be formed in the balloon causing an outer diameter of an axially perpendicular cross section to be enlarged due to a bulge of the turned-back portion of the balloon, and thus, it may be difficult to be inserted into a thin living body lumen. In a case where the outer diameter of the shaft portion is reduced to be able to obtain an expected outer diameter of the axially perpendicular cross section when the balloon is folded, flexural rigidity of the shaft portion is degraded, resulting in degradation of deliverability of a catheter. Regarding a stent delivery system in which a stent is arranged on an outer periphery of the balloon, which is similar to the balloon catheter, concerns that it may be difficult to be inserted into the thin living body lumen or degradation of the deliverability of a catheter can occur.
The present disclosure provides a balloon catheter and a stent delivery system in which high deliverability can be maintained without degrading flexural rigidity of the shaft portion, and can reduce the outer diameter at the time the balloon is folded.